Calcium tartrate

Calcium tartrate is the calcium salt of tartaric acid. It may precipitate in wines during storage, forming an undesirable haze or sediment of small crystals in the bottle that consumers mistake for a fault. Haze stabilization treatments may be required to prevent this problem: winemakers typically use cold stabilization, holding the wine near freezing so tartrates crystallize and can be filtered out before bottling. Although harmless, tartrate crystals are commercially undesirable, so tartrate stability is a standard quality check in winemaking.